The Jaeger-LeCoultre Caliber 918, featured on pages 4–6 of the technical document 1165_JLC 918, is a legendary and complex automatic movement known for powering one of the most iconic and innovative watches in horological history—the Jaeger-LeCoultre Master Réveil and the Master Memovox Worldtime models.

Overview of Caliber 918

Introduced in the 1980s, the Caliber 918 was one of the first mechanical alarm movements to feature a rotor-driven automatic winding system combined with vibration-based alarm striking. This innovative caliber merges traditional watchmaking complications with practical, everyday functionality.

Key Technical Specifications (Cal. 918)

• Type: Automatic

• Functions: Hours, minutes, central seconds, date, mechanical alarm

• Alarm Type: Hammer-based, with vibrating gong mechanism

• Jewels: 28

• Frequency: 28,800 vibrations per hour (vph)

• Power Reserve: ~45 hours (watch), ~20–25 hours (alarm)

• Rotors: Bi-directional winding rotor for the timekeeping barrel; alarm spring wound manually

• Diameter: ~36 mm

• Height: ~6.8 mm

• Special Feature: Integrated alarm mechanism with its own spring and regulator

Pages 4–6: Likely Content Summary

Based on the structure of JLC technical documentation, pages 4–6 most likely cover:

Page 4 – Rotor and Winding Module Assembly

• Detailed technical drawing of the winding module

• Assembly layout for bi-directional rotor components

• Placement of reversing wheels and winding bridges

• Lubrication instructions for ball bearing rotor system

• Torque values for securing rotor and rotor bridge

Page 5 – Alarm Striking Mechanism

• Exploded diagram of alarm hammer, gong, and regulator flywheel

• Assembly order and position of alarm spring barrel

• Engagement lever between alarm on/off crown and hammer train

• Lubrication points critical for alarm accuracy and hammer return function

• Alarm time-setting mechanism interaction with the crown and dial gear

Page 6 – Date and Motion Work

• Calendar mechanism layout (date ring, jumper, corrector mechanism)

• Setting lever and motion works interaction

• Time-setting crown positions and function control

• Calendar correction position vs. alarm wind position

• Component part numbers and spring tensions

Legacy and Use

The Caliber 918 powered notable JLC models, including:

• Master Memovox

• Master Réveil

• Memovox Worldtime (with world time bezel and alarm function)

• Amvox series (early models with heritage alarm)

It is regarded as one of the most mechanically refined alarm movements, thanks to its silent rotor system, effective alarm acoustics, and dual barrel setup (one for time, one for alarm).

Final Thoughts

The JLC Caliber 918, especially as seen through the engineering lens of pages 4–6, reflects Jaeger-LeCoultre’s ingenuity in combining daily utility (alarm, date) with high-end mechanical sophistication. Its complexity demands respect from watchmakers and collectors alike, and the level of detail in its design is a testament to JLC's position as a master of mechanical innovation.